1. Field of the Invention
The present invention relates to a focus lens apparatus which performs a focus operation with a depth of focus taken into account.
2. Description of the Related Art
In a conventional autofocus system, as described in U.S. Pat. No. 5,486,860, a focus adjustment is performed on all subjects within an area for recognizing the focus state to continuously maintain an in-focus state. Therefore, the focus adjustment is performed to maintain the focus state during a zooming operation of a zoom lens.
When the focus adjustment is to be performed on a specific subject among multiple subjects located within a screen at a wide-angle end, it is difficult to perform a high-precision focus adjustment on the specific subject due to the deep depth of focus.
The conventional autofocus system performs a focus adjustment to maintain the in-focus state averagely for all the subjects within the area for recognizing the focus state. Therefore, if multiple subjects are within the area for recognizing the focus state, it is difficult to perform the focus adjustment particularly on the specific subject among the subjects.
A high-precision focus adjustment may be automatically performed in a case in which only a specific subject can be captured within the area for recognizing the focus state by use of a telephoto side of the zoom lens. However, when the zoom lens is moved to a wide-angle side, the focus adjustment is performed again, and hence the focus adjustment cannot be performed on the specific subject similarly.